Stratospheric Water Vapor beyond NASA’s Aura MLS: Assimilating SAGE
III/ISS profiles for a continued climate record
Abstract
Stratospheric water vapor (SWV) is a greenhouse gas that has a
significant, yet uncertain, impact on the Earth’s climate through its
radiative effect and feedback. As the climate changes, it is thus
critical to monitor and understand changes in SWV. NASA’s Microwave Limb
Sounder (MLS) aboard the Aura satellite has observed SWV since 2004 but
will soon reach end of life. The Stratospheric Aerosol and Gas
Experiment (SAGE) missions observe SWV as well, with the SAGE III
instrument operating on the International Space Station (ISS) since
2017. We use the constituent data assimilation capabilities of NASA’s
Goddard Earth Observing System (GEOS) to demonstrate that the up to 30
SAGE III/ISS profiles each day provide a useful constraint on SWV from
500 to 1500 K over the observed midlatitudes and tropics. We conclude
that by assimilating SAGE III/ISS SWV into GEOS we can continue to
monitor SWV after Aura MLS.